The invention pertains to roadways, particularly elevated roadways, and more particularly concerns the interface of vehicle wheels and an elevated vertical roadway along which a vehicle moves, and the provision of improved vehicle/roadway interaction providing more traction than using vehicle weight would allow, allowing steeper roadway grade, improved roadway lifetime, reduced construction and maintenance expense, higher vehicle acceleration and deceleration, and a smoother vehicle ride.
The most common means for establishing adequate traction of the vehicle drive wheels against a roadway has been the reliance upon the weight of the vehicle, pressing each wheel against the roadway with sufficient force to allow adequate traction. Though this conventional approach has of course been exploited to great advantage, it exhibits problems addressed by the present invention.
Since, in the conventional approach, the maximum traction which can be maintained depends upon the component of the vehicle weight force acting perpendicular to the roadway, if the roadway grade becomes too steep, the vehicle drive wheels will slip.
And even on a level grade, there will be drive wheel slippage in the case of vehicle acceleration or deceleration demanding traction greater than that allowed by the vehicle weight.
More importantly, dependence upon very heavy vehicles to attain adequate traction, results in a high rate of roadway damage and required roadway repair and maintenance expense, and reduced roadway lifetime, as roadways are damaged by the heavy vehicles they carry, in large part because of oscillations of the vehicle""s wheels against the roadway. This could be greatly reduced if improved traction could be obtained by means independent of vehicle weight, so that vehicles lighter than conventional ones could successfully be used, and if oscillations of the wheels against the roadway could be nearly eliminated.
So two needs met by the present invention are the need for means to establish improved vehicle-wheel-to-roadway traction independently of vehicle weight and the need for means to greatly reduce the oscillation of vehicle wheels against the roadway.
Another problem of the conventional roadway/vehicle interface is that wheel oscillations cause not only a high rate of roadway damage, but also an irregular, bumpy vehicle ride, displeasing to paying passengers.
So another need not met by the conventional approach but addressed by the present invention, is the provision of means which allow maintenance of a smooth vehicle ride with relatively little wheel oscillations.
These needs are met in the present invention, by the combination of an advantageous roadway and vehicle wheel interface geometry, and a traction affording means which also serves substantially to prevent vehicle wheel oscillations. The interface geometry is formed by a vertical roadway having normally mirror-image vertical sides that each have a slightly concave portion between two flat portions and that receive the convex wheel rims with each wheel being passively steerable and mounted on a vertical axle attached to the vehicle, with the width of the wheel rim being equal to or less than the width of the convex portion of the roadway. The traction affording means is a compression means for causing the wheel rims to be in strong compression against the convex portion of the vertical sides of the roadway. The compression force acting upon each wheel exceeds the weight supported against gravity by that wheel. Thus more traction is available than may be obtained by using vehicle weight.
It is readily seen that the combined effects of the interface geometry and compression means are to not only afford superior traction between the wheel and roadway, but to also cause the wheels to stay substantially centered in the thinnest part of the roadway, with minimum oscillations against it.
Since the amount of traction which may be developed between the wheel rim and the roadway depends not only upon the force urging the wheel against the roadway but also upon the coefficient of friction between them, the present invention in some embodiments, has wheel rims formed of composite materials that offer a high coefficient of friction. In other embodiments the wheel rims are formed of steel because steel wheels on a steel roadway offer the lowest thrust loss to rolling friction.
The invention is an apparatus for the interface of a vehicle""s wheels and an elevated roadway, for achieving more traction than that possible by using the vehicle""s weight, and for minimizing vehicle wheel oscillation against the roadway. Said apparatus has a roadway/wheel interface geometry comprising a roadway with normally at least substantially vertical and normally mirror image sides, with said sides each having slightly concave portions, and slightly convex wheel rims of horizontal vehicle wheels rolling along said concave portions of the roadway sides, with said wheels normally being passively steerable and rotating about at least substantially vertical axles secured to the vehicle, said wheel rims having a width equal to or less than the width of the concave portion of the roadway sides; and said apparatus having a compression means, independent of vehicle weight, for causing the wheels to be in substantial compression against the sides of the roadway. In one embodiment said compression means comprises the combination of pairs of parallel wheel axles on opposite sides of the roadway, and cables in substantial tension around each said pair of axles. One embodiment of the invention further comprises use of light weight wheels formed principally of aluminum with rims of composite material such as that used in conventional auto tires, offering a high coefficient of friction. Another embodiment also comprises use of lightweight wheels but with rims of steel which minimize loss of thrust to rolling friction.